How did Hillary Clinton blow a 7-percentage-point lead over Donald Trump in the final month of the campaign? Much of the post-election analysis has revolved around FBI Director James Comey’s letter to Congress on Oct. 28. Less attention was spent on the role that WikiLeaks played. Until, that is, news broke that the CIA thought Russia actively tried to help Trump win; figures connected to the Russian government allegedly hacked Clinton campaign chairman John Podesta’s emails, which then found their way to WikiLeaks. So what effect did WikiLeaks have on the election?
The drip, drip, drip of the hacked emails — published weekly during October — makes it all but impossible to measure their effect precisely. So much else happened during the final weeks of the campaign — the “Access Hollywood” tape, the Comey letter, the debates, etc. But we can say two things: (i) Americans were interested in the WikiLeaks releases, and (ii) the timeline of Clinton’s fall in the polls roughly matches the emails’ publishing schedule.
First, Americans were clearly paying attention to the WikiLeaks releases, despite all the other craziness in those final weeks. We can see this using Google Trends, a useful tool in this instance because it gives us a rough sense for what people, rather than the press, were focusing on.
WikiLeaks was almost exclusively an October story. Over 72 percent of people who searched for WikiLeaks from June onward did so during October or the first week of November. Interest really got going with Julian Assange’s press conference on Oct. 4 announcing that there would be more information coming from WikiLeaks about the election. From there, it was a steady barrage. In contrast, only about 40 percent of searches involving Clinton and Trump in general from June onward came in October or the first week of November. Just over 50 percent of searches for Comey specifically happened during this period.
In fact, searches for WikiLeaks from the beginning of October through Election Day were about double the searches for the FBI. When Comey’s letter to Congress was released, search for the FBI spiked above WikiLeaks, but then fell quickly. In the final week of the campaign, WikiLeaks beat the FBI every day.1
Now, Clinton’s drop in the polls doesn’t line up perfectly with the surge in WikiLeaks interest. When WikiLeaks had its highest search day in early October, Clinton’s poll numbers were rising. They continued to go up for another two weeks, even as WikiLeaks was releasing emails. That is, there isn’t one pivotal “aha!” point which shows that WikiLeaks caused Clinton’s numbers to drop. That said, the race was tightening before Comey ever sent his letter to Congress in late October. Clinton’s lead over Trump peaked at 7 percentage points on Oct. 17, according to the FiveThirtyEight polls-only forecast. By the time Comey released his letter, it was down to 5.7 percentage points. It’s also possible that Clinton’s numbers would have risen even further in early October had it not been for WikiLeaks. Trump had to fight off both bad debate performances and the release of the “Access Hollywood” tape.
There just isn’t a clean-cut story in the data. For instance, you might have expected a decline in the percentage of Americans who trusted Clinton after WikiLeaks began its releases. As Politico’s Ken Vogel pointed out in mid-October, both Trump campaign officials and even progressives said the WikiLeaks emails revealed that Clinton would be “compromised” if she became president. But the percentage of Americans who found Clinton to be honest or trustworthy stayed at around 30 percent in polling throughout October and into November.
The evidence that WikiLeaks had an impact, therefore, is circumstantial. Trump, for instance, won among voters who decided who to vote for in October 51 percent to 37 percent, according to national exit polls. That’s Trump’s best time period. He carried voters who decided in the final week, when you might expect Comey’s letter to have had the largest impact, 45 percent to 42 percent. (Although, Trump’s margin among those who decided in the final week was wider in the exit polls in some crucial swing states.) And while Clinton’s lead was dropping in the FiveThirtyEight polls-only forecast before the Comey letter was released, the drop accelerated slightly afterward.
Of course, one thing didn’t sink Clinton. The evidence suggests WikiLeaks is among the factors that might have contributed to her loss, but we really can’t say much more than that.